Secondary Ion Mass Spectrometry Bias on Isotope Ratios in Dolomite–Ankerite,Part II: δ13C Matrix Effects |
| |
| Authors: | Maciej G ?liwiński Kouki Kitajima Reinhard Kozdon Michael J Spicuzza John H Fournelle Adam Denny John W Valley |
| |
| Institution: | 1. WiscSIMS, Department of Geoscience, University of Wisconsin‐Madison, Madison, WI, USA;2. Department of Geoscience, University of Wisconsin‐Madison, Madison, WI, USA;3. NASA Astrobiology Institute, Department of Geoscience, University of Wisconsin‐Madison, Madison, WI, USA;4. Lamont‐Doherty Earth Observatory of Columbia University, Palisades, NY, USA |
| |
| Abstract: | This study is Part II of a series that documents the development of a suite of calibration reference materials for in situ SIMS analysis of stable isotope ratios in Ca‐Mg‐Fe carbonates. Part I explored the effects of Fe2+ substitution on SIMS δ18O bias measured from the dolomite–ankerite solid solution series CaMg(CO3)2–CaFe(CO3)2], whereas this complementary work explores the compositional dependence of SIMS δ13C bias (calibrated range: Fe# = 0.004–0.789, where Fe# = molar Fe/(Mg+Fe)). Under routine operating conditions for carbonate δ13C analysis at WiscSIMS (CAMECA IMS 1280), the magnitude of instrumental bias increased exponentially by 2.5–5.5‰ (session‐specific) with increasing Fe‐content in the dolomite structure, but appeared insensitive to minor Mn substitution < 2.6 mole % Mn/(Ca+Mg+Fe+Mn)]. The compositional dependence of bias (i.e., the matrix effect) was expressed using the Hill equation, yielding calibration residual values ≤ 0.3‰ relative to CRM NBS‐19 for eleven carbonate reference materials (6‐μm‐diameter spot size measurements). Based on the spot‐to‐spot repeatability of a drift monitor material that ‘bracketed’ each set of ten sample‐spot analyses, the analytical precision was ± 0.6–1.2‰ (2s, standard deviations). The analytical uncertainty for individual sample analyses was approximated by combining the precision and calibration residual values (propagated in quadrature), suggesting an uncertainty of ± 1.0–1.5‰ (2s). |
| |
| Keywords: |
SIMS
carbon isotopes dolomite ankerite matrix effects
SIMS
isotopes du carbone dolomite anké rite effets de matrice |
|
|
